If it seems like a fishy player and I put them on a draw, I often continue my betting drive through the river:

***** Hand History for Game 2831345470 *****
$25 NL Texas Hold'em - Wednesday, October 05, 19:39:50 EDT 2005
Table Table 37152 (Real Money)
Seat 9 is the button
Total number of players : 10
Seat 3: cleve2005 ( $40.05 )
Seat 4: wagerchen ( $3.45 )
Seat 5: hobski ( $44.60 )
Seat 7: CAB52111 ( $145.88 )
Seat 8: Zangief00 ( $35.50 )
Seat 10: sharko34 ( $12.71 )
Seat 9: snoopy_ace ( $10.75 )
Seat 6: PSUalumnut ( $4.60 )
Seat 2: cliveelk ( $16.70 )
Seat 1: joelteb ( $23.25 )
sharko34 posts small blind [$0.10].
joelteb posts big blind [$0.25].
** Dealing down cards **
Dealt to Zangief00 [ 9s Ks ]
cliveelk calls [$0.25].
wagerchen folds.
hobski folds.
PSUalumnut folds.
CAB52111 calls [$0.25].
Zangief00 calls [$0.25].
snoopy_ace folds.
sharko34 folds.
joelteb checks.
** Dealing Flop ** [ Qh, Js, 6s ]
joelteb: nh
joelteb checks.
cliveelk checks.
CAB52111 checks.
Zangief00 bets [$1].
joelteb folds.
cliveelk calls [$1].
CAB52111 folds.
** Dealing Turn ** [ Jh ]
cliveelk checks.
Zangief00 bets [$3].
cliveelk calls [$3].
** Dealing River ** [ 2d ]
cliveelk checks.
Zangief00 bets [$5].
cliveelk folds.
Zangief00 does not show cards.

I think he calls me on the river here way less than 50% of the time, making it quite profitable.